The mass space transit system of course. Space buses, space trains... :P
The First Gen Ancients are 4-d beings so we know nothing about them. Most believe they don't even exist. But if they do, then travel means nothing to them and they move freely between dimensions. In this story I only deal with the 2nd Gen Ancients and 3rd Gen beings.

What you are referring to is called "Population I, II, and III Stars" which deals with the amount of heavier elements or metals they contain. It's actually scaled backwards in that the youngest stars that contain the most metals are called Population I. The very first stars, Population III, (a population of huge stars that formed the first 26 elements via nucleosynthesis) that had no metals at all have theoretically been destroyed in supernovae.

For this story the terms "First and Second Generation Ancients" are purely fictional and the generations are meant to represent only the generations of stars with solar systems that can sustain life.

Edit: Jamie you're right. I see what you're pointing out now. I got it screwed up so I'm going to have to fix this page.
Edit: fixed